Strut construction

ABSTRACT

A strut construction having outer and inner telescoping strut members capable of relative extending and collapsing movements. The outer strut member has a socket for a locking piece which is captive but moveable therein. A release member is captive and slidable on the strut construction between locking and release positions. The release member has spaced-apart shallow and deep internal pockets for respectively receiving, depending on its locking or releasing position, portions of the captive locking piece in the outer strut member. The inner strut member has a shoulder which provides shallow and deep pockets to respectively receive other portions of the captive locking piece. The captive locking piece, socket of the outer strut member, and the shoulder restrict movement of the release member and restrict full telescoping collapsing movement of the strut members when the release member is in its locking position wherein portions of the locking piece occupy the shallow pockets of the release member and shoulder, and alternatively enable full telescoping collapsing movement of the strut members to be effected when the release member is in its releasing position and portions of the locking piece occupy the deep pocket of the release member.

CROSS REFERENCES TO RELATED APPLICATIONS

1. Co-pending application U.S. Ser. No. 08/014,535 filed Feb. 8, 1993, and having common ownership with the present application.

2. The present application is a continuation-in-part of co-pending application U.S. Ser. No. 07/970,016 filed Nov. 2, 1992, and having common ownership with the present application now U.S. Pat. No. 5,265,970.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT

Research and development of the present invention and application have not been Federally-sponsored, and no rights are given under any Federal program.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

This invention relates to collapsible strut constructions, and more particularly to such constructions wherein telescoping strut members are lockable in extended positions.

DESCRIPTION OF THE RELATED ART INCLUDING INFORMATION DISCLOSED UNDER 37 CFR §§1.97-1.99

The following prior art references are hereby cited as being of interest.

    ______________________________________                                         U.S. Pats. Nos.:                                                               ______________________________________                                         3,367,689      3,390,874                                                                               3,442,541                                              3,469,871      4,014,467                                                                               4,362,415                                              4,366,945      4,453,449                                                                               4,453,748                                              4,546,956      4,682,795                                                                               4,960,344                                              5,066,049                                                                      ______________________________________                                    

U.S. Pat. No. 3,442,541, FIG. 1, discloses a releasable fastener in the form of a strut having telescoping inner and outer members, and a locking sleeve which is slidable on the outer member and which controls movement of locking dogs carried respectively in radial slots in the outer member. The inner member has a series of transverse locking ribs which are engaged by corresponding locking ribs on the dogs. With the locking sleeve in its locked position, the dogs are in forcible locking engagement with the ribs on the inner member. When it is desired to release the strut, the sleeve is shifted axially to a position wherein the locking dogs can shift outwardly in response to axial force applied between the telescoping members, and the latter can thereafter collapse into one another, as desired.

U.S. Pat. No. 3,469,871 illustrates a lockable coupling having telescoping inner and outer members and which employs two arcuate locking dogs carried in a circumferential groove of the inner member, and also employs multiple force-transmitting balls housed in radial slots of the inner member. Each arcuate locking dog is engaged by two balls. In operation, a release member or rod having a conical actuator portion engages the balls and shifts them radially, along with the arcuate locking dogs. During locking, the dogs are shifted laterally into inner annular grooves on the outer telescoping member. Locking and release of the telescoping members is accomplished by axially displacing the release member, via a pin-coupled release collar or release member (64, FIG. 2) carried by the inner telescoping member.

Other constructions involving struts of the type employing radially shiftable locking components are illustrated in U.S. Pat. No. 3,390,874 and U.S. Pat. No. 3,367,689.

U.S. Pat. No. 4,362,415 illustrates a locking strut having a slidable locking collar which can be positively retained in a locking position by an external spring-biased locking lever.

Less pertinent is U.S. Pat. No. 4,546,956, which discloses a releasable coupling for a hose attachable to a supply of compressed gas. The arrangement is such that the coupling cannot be removed from the supply fitting until after the pressure is reduced, to minimize danger to personnel from an inadvertent, gas-propelled "fly off" of the coupling. Although this device provides a safety interlock feature, it is not a strut, and the structure and mode of operation of the device is different from that of the invention, as will be apparent hereinbelow.

U.S. Pat. Nos. 4,014,467; 4,366,945; 4,453,748; 4,682,795; and 5,066,049 all involve releasable hose fittings/couplings having various types of locking structures that employ captive balls.

U.S. Pat. No. 4,960,344 discloses a coupling between a drive shaft and a driven shaft. U.S. Pat. No. 4,453,449 relates to a re-useable, non-destructive hold-down apparatus employing locking balls, which apparatus grips a member such as a missile or projectile, until a certain tension is developed by the same, and which thereafter releases the member suddenly.

In connection with those of the above patents dealing with struts, there existed significant problems involving inadvertent release under load. Specifically, with either compressive or tensile loads applied between the telescoping members of the prior art struts, there was a danger that the operator could slide the locking collar (or other release mechanism) to a release position while the strut was still under load, possibly leading to a sudden collapse of the strut and an accompanying uncontrollable swing or fall of the member being held, by virtue of its own weight. Such a condition was capable of causing serious injury to either the operator or to other personnel in the area.

In the past, struts of the type noted have been used with aircraft cowlings, in order to retain the cowlings in an open position as during maintenance and/or servicing of the aircraft engines. Depending on the size of the aircraft, such cowlings can weigh many hundreds of pounds, and the potential of injury resulting from being struck by an inadvertently released cowling can be readily appreciated if one considers structures of such magnitude and size.

SUMMARY OF THE INVENTION

The above disadvantages and drawbacks of prior locking strut constructions are obviated by the present invention, which has for one object the provision of a locking strut which positively resists release at such time as any load is applied between its telescoping inner and outer members, thereby requiring that an operator first manually (or with equipment) take control of the load between such members, and thereafter substantially completely remove such load, prior to manually shifting of a locking sleeve or release member of the strut towards its release position.

A related object of the invention is to provide an improved locking strut as above characterized, wherein greatly improved safety of operation is realized, by elimination of the possibility of an operator being inadvertently struck by a falling structural component connected with the strut.

Still another object of the invention is to provide an improved locking strut in accordance with the foregoing, where the strut can be readily adapted, by means of a simple modification, to handle either compressive loads or tensile loads, thus providing maximum flexibility to an installation of a type incorporating such a strut.

Yet another object of the invention is to provide an improved strut as above set forth, which is both simple in its structure, and rugged and reliable over extended periods of use.

A still further object of the invention is to provide an improved strut of the kind indicated, wherein little or no maintenance or servicing is required over the life of the strut.

Yet another object of the invention is to provide an improved strut as outlined above, wherein the strut components can be readily fabricated and assembled, so as to keep the manufacturing costs as low as possible.

A further object of the invention is to provide improved strut constructions as above characterized, which can take the form of relatively simple structures incorporating as locking pieces, balls that are economical to fabricate and especially applicable for use with relatively light loads, or alternately take the form of slightly more complex structures involving arcuate locking dogs at somewhat higher cost, but which provide significantly improved operation over extended periods of time and with relatively higher operating loads.

The above objects are accomplished by a strut construction comprising, in combination outer and inner strut members having extending and collapsing movements, the outer strut member having a socket, a locking piece captive and moveable in the socket, and a release member moveable on the strut between locking and releasing positions. The release member has a shallow and a deep pocket for respectively receiving, depending on its locking or releasing position, a portion of the locking piece. The inner strut member has a shallow and a deep pocket to respectively receive another portion of the locking piece. The locking piece, socket of the outer strut member, and shallow pocket of the inner strut member restrict movement of the release member and also restrict collapsing movement of the strut members when the release member is in its locking position wherein portions of the locking piece occupy the shallow pockets of both the release member and inner strut member, and alternatively enable full collapsing movement of the strut members to be effected when the release member is in its releasing position and portions of the locking piece occupy the deep pocket of the release member. The pockets of the inner strut member enable a limited relative movement of the strut members to be had for the purpose of freeing the locking piece for movement into the deep pocket of the inner strut member so as to enable the release member to be shifted from its locking position to its releasing position, for permitting collapse of the strut.

The objects are further accomplished by a strut construction comprising in combination first and second strut members capable of relative movement between extended and collapsed positions, the first strut member having a socket and having a locking piece which is held captive in and which is moveable in the socket, and a release member held captive and slidable on the strut construction between locking and release positions, the release member having a projecting shoulder adjacent to the socket. In addition, camming shoulder means are provided on the second strut member, normally holding the locking piece in a position in the socket so as to block the projecting shoulder of the release member and prevent releasing movement of the release member when the strut members are in extended position and under load. The camming shoulder means can release the locking piece for unblocking movement thereof in the socket in response to relative movement of the strut members in a direction in opposition to the load thereon, thereby to unblock the projecting shoulder of the release member and enable releasing movement thereof.

The arrangement is such that prior to release of the release member, the load on the strut, be it tensile or compressive, must first be manually removed by the operator and thereafter the strut momentarily extended or retracted a short distance, as by grasping and moving one of the components being held by the strut, following which the release member can be manually slid toward a releasing position under the condition of essentially zero load on the strut members.

Significantly improved operational safety is realized, since the operator cannot inadvertently slide the release member toward a release position unless the load on the strut has first been essentially completely removed, and the strut members thereafter moved slightly in a direction, with respect to one another, which is opposite to that of the load.

Other features and advantages will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary view, partly in side elevation and partly in axial section, of an improved locking strut constructed in accordance with the principles of the present invention, illustrating telescoping inner and outer strut members having applied thereto a compressive load, and showing locking balls and a release collar or release member having an internal shallow pocket and an internal deep pocket, the release collar or release member being disposed in its locked position.

FIG. 2 is a view like FIG. 1, except with the load having been removed from the strut, and showing the strut members thereafter extended by a short distance wherein a deep pocket in the inner member is brought to a position registering with the locking balls, and in preparation for sliding of the release collar or release member.

FIG. 3 is a view like FIGS. 1 and 2, except showing the locking balls mostly occupying the deep pocket and wherein the release collar or release member has been manually shifted toward the left with respect to the outer strut member.

FIG. 4 is a view like FIGS. 1-3, except showing the locking balls displaced radially outward and occupying the deep pocket in the release collar or release member, the balls slidably engaging the outer cylindrical surface of the inner strut member.

FIG. 5 is a view like FIGS. 1-4, except illustrating a modified strut construction of a type adapted for use with tensile forces applied respectively to telescoping inner and outer strut members.

FIG. 6 is an enlarged diagrammatic representation of the strut of FIGS. 1-4, showing one locking ball held captive in a radial slot of the outer strut member, and showing a camming shoulder of a shallow pocket of the inner strut member urging the ball radially outward into forcible engagement with the internal shallow pocket of the release collar or release member.

FIG. 7 is an enlarged diagrammatic representation like FIG. 6, except showing a manual extension of the inner and outer strut members as permitted by the compressive load thereon having been removed, such that the inner strut member can be moved so that its deep pocket registers with one locking ball and provides clearance for the ball to move radially inward during manual shifting of the release collar or release member.

FIG. 8 is an enlarged diagrammatic representation like FIGS. 6 and 7, except showing the ball seated in the deep pocket of the inner strut member. The release collar or release member has been manually shifted axially toward the left with respect to the outer strut member, to its unlocking position and held there. The ball registers with the deep internal pocket of the release collar or release member.

FIG. 9 is an enlarged diagrammatic representation like FIGS. 6-8, except showing the inner strut member having been collapsed, and wherein the ball has been shifted radially outward, by virtue of its engagement with the smooth cylindrical surface of the inner strut member, to a position occupying the deep internal pocket of the release collar or release member. The release collar or release member remains in this unlocking position even following its manual release.

FIG. 10 is a fragmentary axial section of still another embodiment of the invention, illustrating a modified strut incorporating arcuate locking pieces, and providing improved performance for certain applications involving repeated operations and relatively high load capacities.

FIG. 11 is a transverse section taken on the line 11--11 of FIG. 10.

FIG. 12 is a front elevation of one of the locking pieces of the strut of FIGS. 10 and 11.

FIG. 13 is a top plan view of the locking piece of FIG. 12, and

FIG. 14 is a transverse section taken on the line 14--14 of FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 6 there is illustrated an extendable and collapsible strut construction generally designated by the numeral 10, comprising an inner strut member 12 and an outer strut member 14, the inner member 12 being adapted to telescope into the outer member 14 in the usual manner during collapse of the strut 10.

The outer member 14 is shown as comprising a bearing end fitting 16 having a hole 18 to receive a suitable bearing member or pin (not shown), and comprising a tubular body part 20 and a cage 22 having an external thread which mates with corresponding internal threads of the body part 20. This cage has four circumferentially spaced holes 24, FIGS. 1 and 6, constituting sockets which respectively carry and hold captive four locking pieces comprising balls 26, two of which are shown in FIG. 1 in solid outline, and one of which is shown in dotted outline.

The inner strut member 12 comprises a tubular part 28 having at its one end, a clasp fitting or coupling 30, shown as being of a type having an oblique pin-receiving slot and retractable locking dog. At its inner end, the inner strut member 12 has a threaded locking adapter or fitting 32, screwed into the adjacent end of the tubular part 28.

Slidably carried on the outer strut member 14 is a tubular release collar or release member 34 having a cylindrical bearing portion 36 which is adapted for sliding engagement with the corresponding cylindrical surface of the cage 22. A spiral compression spring 38 is disposed between the release collar or release member 34 and the outer strut member 14, to normally bias the collar or release member 34 toward the right in FIG. 1. The release collar or release member alternatively can have a collar insert 40, shown in dotted outline in FIGS. 1-4, and there is an internal annular recess in the release collar or release member 34 that carries a sealing member 42, to prevent ingress of dust or foreign matter to the area between the outer strut member 14 and the release collar or release member. A second seal 44 is provided, carried in an external annular recess of the cage 22 of the outer strut member 14. The release collar or release member 34 is held captive on the outer strut member 14 by a retaining ring 46 snapped into a groove in one end, and by the spring 38. A stop spacer 50 is optionally provided, carried on the outer strut member 14 and inside the spring 38, to limit the extent of travel of the release collar or release member 34 in one direction and also avoid overcompression of the spring. A snap ring 63 engaging a shoulder 64 constitutes a stop for the members 12 and 14.

In accordance with the present invention there is provided on the inner strut member 12 and on the release collar or release member 34, a new combination involving cooperable structures which effectively transmit to the release collar or release member 34, load or force which is applied between the inner and outer strut members 12, 14, and which structures operate to forcibly retain the collar or release member 34 against any axial movement with respect to the outer strut member 14, until such time as the load between the strut members 12, 14 is essentially completely removed. In accomplishing this retention of the release collar or release member 34, there are provided on the outer surface of the inner strut member 12 a shoulder means 52 formed between a shallow pocket 54 and a deep pocket 56, the shallow pocket 54 extending axially for a somewhat greater distance measured along the inner strut member 12. There are also provided on the release collar or release member 34, a shallow internal pocket 58 in the form of an annular internal groove, and a deep internal pocket 60 also in the form of an annular internal groove, displaced axially from the shallow internal pocket 58 of the collar or release member 34. Separating the pockets is an annular internal shoulder 62. The pockets can be formed in the insert 40 if such is used, which is first machined as a separate piece, and then pressed into an end recess in the body of the release collar or release member 34. Depending on the locking or release condition of the strut, the four balls 26 become seated in various ones of the pockets 54, 56, 58, 60 in order to achieve the desired locking or release function.

In the embodiment shown in FIGS. 1-4, the strut 10 is of a type which is extendable to a predetermined length, and thereafter locked in an extended position. The extended strut is especially adapted to remain locked so long as a compressive load is applied between the outer strut member 14 and the inner strut member 12. The retaining ring 63 carried on the inner strut member 12 constitutes a stop means, and limits the extent of travel of the inner strut member by its engagement with the internal shoulder in the cage 22.

In describing the operation of the improved strut of the present invention, reference is initially made to FIGS. 1-4, and FIGS. 6-9. In FIGS. 1 and 6, the strut is in a locked condition, wherein the inner and outer strut members 12, 14, respectively are almost fully extended. As shown, the balls 26 occupy the holes or sockets 24 in the cage 22, and the shallow pocket 54 of the inner strut member 12 is in engagement with the balls 26. The balls 26 also engage the shallow internal pocket 58 of the release collar or release member 34. By the invention, a compressive force applied between the outer and inner strut members 14, 12 respectively causes the balls 26 to be cammed or urged radially outwardly into forcible engagement with the walls of the shallow internal pocket 58 of the release collar or release member 34. Under such circumstances, the release collar or release member 34 is held fast against inadvertent axial movement, and more particularly against any such movement toward the left in FIG. 1, with respect to the outer strut member 14. As long as the compressive load remains applied, the release collar or release member 34 is immovable, and it is this feature of immovability of the release collar or release member 34 under strut load, which gives rise to the improved safety of operation of the strut as compared to known arrangements. Stated differently, with known prior strut constructions, a slide or release collar or release member was normally capable of being axially shifted, whether intentional or inadvertent, in the presence of load applied to the strut members. Where the load was considerable, a sudden collapse of the strut could occur, and possibly cause serious injury to the operator.

In contrast, with the present invention, the release collar or release member 34 cannot be moved, either intentionally or accidentally, until the load is first removed from members 12 and 14, and thereafter the members manually extended with respect to one another by a short distance. More particularly, with reference to FIGS. 2 and 7, the first step in unlocking the strut is to remove the load, which is done manually by the operator, by grasping one of the load-generating components (not shown) to which the strut is attached and applying the necessary force to relieve the compression. Then, the strut members 12, 14 are manually extended a short distance with respect to one another, as in FIGS. 2 and 7, so as to axially align the deep pocket 56 of the inner strut member 12 with the balls 26, which in effect provides a clearance space in the inner strut member 12 into which the balls 26 can be moved as the release collar or release member 34 is shifted. Since the balls 26 no longer occupy the shallow pocket 58, the release collar or release member 34 is freed, and the operator, with his other hand, shifts the collar or release member 34 toward the left as in FIGS. 3 and 8, wherein the deep internal pocket 60 of the release collar or release member 34 overlies the balls 26. In FIGS. 4 and 9, following partial manual collapse of the strut members, the balls 26 become disposed between the walls of the internal deep pocket 60 of the release collar or release member 34 and the smooth cylindrical surface of the part 28 of the inner strut member 12. From this position, the inner strut member 12 can be further moved toward the left, to a fully collapsed condition (not shown).

In order to effect subsequent extension of the strut, the inner strut member 12 is manually withdrawn from the outer strut member 14, past the relative positions of FIG. 4, until the deep pocket 56 of the inner strut member 12 underlies the balls 26. At this time, the balls 26 are shifted radially inwardly under the action of the spring-biased release collar or release member 34, which can now snap to the right, FIG. 2, wherein the shallow internal pocket 58 of the release collar or release member 34 overlies the balls 26. The inner strut member 12 then is collapsed slightly until the shoulder 52 of the inner strut member 12 underlies the balls, the parts ultimately being returned to the relative positions shown in FIG. 1. The strut is now locked in an extended position, and can accept compressive loads. As long as there is a compressive force applied between the outer and inner strut members, the release collar or release member remains forcibly restrained against any axial movement as a consequence of an applied force to the collar or release member, whether intentional or inadvertent.

The disclosed construction has been assigned by the applicant, the acronym "NULU", which stands for "no unlock under load".

The improved strut as set forth above has the important advantage of providing significantly improved safety of operation. As noted previously, where such a strut is employed to hold an aircraft cowling in a raised position, as during inspection or servicing of an aircraft engine, the strut of the present invention prevents inadvertent release or slipping of the cowling. In particular, in order to lower the cowling to its operative position, the operator must first grasp it and apply to the strut, a force opposite in direction to that applied by the cowling, and thereafter extend the strut by a slight distance; while holding the cowling, the operator then slides the release collar or release member, with his other hand, toward its release position and then slowly lowers the cowling to collapse the strut. In other words, the operator must take control of the load before the release collar or release member can be shifted to unlock the strut. The deliberation required by the operator in carrying out this sequence of steps, involving first taking control of the load and then shifting the release collar or release member to its unlocking position while still holding the load, is considered to be highly significant from the standpoint of safety, and reliable operation.

Another embodiment of the invention is illustrated in FIG. 5, wherein components corresponding to those of FIGS. 1-4 have been designated with the same reference numerals, and modified components assigned like reference numerals with the suffix "a" applied.

In FIG. 5, the relative positions of the shallow and deep pockets 54a, 56a, respectively in the locking adapter 32a of the inner strut member 12 have been reversed from the positions of FIGS. 1-4. Specifically, the construction illustrated in FIG. 5 is intended for use with tensile loads applied between the inner and outer strut members 12, 14.

In accordance with the present invention there is provided on the inner strut member 12 and on the release collar or release member 34, a new combination involving cooperable structures which effectively transmit to the release collar or release member 34, load or force which is applied between the inner and outer strut members 12, 14, and which structures operate to forcibly retain the collar or release member 34 against any axial movement with respect to the outer strut member 14, until such time as the load between the strut members 12, 14 is essentially completely removed. Assuming in FIG. 5 that there exists a tensile load between the strut members 12, 14, the balls 26a are forcibly engaged with the surface of the shallow pocket 58 of the release collar or release member 34. Specifically, the shoulder 62 between the pockets 58, 60 positively prevents axial shifting of the release collar or release member 34, particularly toward the left in FIG. 5, because the balls 26a are held in radially outward positions by the inner strut member 12, and the balls 26a lie in the line or path of travel that the shoulder 62 (FIGS. 1-4) would normally take were the release collar or release member 34 to be moved toward the left, i.e. toward its releasing position. The balls 26a thus block the shoulder 62 in the manner of a locking bolt of a door latch. Before the strut can be unlocked from this extended position, it is necessary to first remove the tensile load between the strut members 12, 14, and thereafter slightly collapse the members by a small distance, wherein the deep pocket 56a of the inner strut member 12 underlies the balls 26a (corresponding to FIGS. 2 and 7 of the first embodiment). Due to the clearance space for the balls that is provided by the deep pocket 56a of the inner strut member 12, the balls 26a can be shifted inwardly by moving the release collar or release member 34 toward the left in FIG. 5, to the position wherein the deep pocket 60 of the release collar or release member 34 overlies the balls 26a (corresponding to FIGS. 3 and 8 of the first embodiment). Then, with the release collar or release member 34 held in its release position, the inner strut member 12 can be telescoped into the outer strut member 14 (corresponding to FIGS. 4 and 9 of the first embodiment), with the balls 26a slidably engaging the smooth cylindrical surface of the inner strut member 12 as the telescoping movement occurs.

Subsequent extension of the strut of FIG. 5 is accomplished by merely forcibly extending the inner strut member 12 (moving it toward the right in FIG. 5) with respect to the outer strut member 14, until the shallow pocket 54a of the inner member 12 arrives at the position of FIG. 5. As the deep pocket 56a of the inner strut member 12 passes beneath the balls 26a, it provides a clearance space for the balls 26a and enables them to be momentarily shifted inwardly sufficiently to allow the spring-biased release collar or release member 34 to spring toward the right, i.e. toward the locking position shown in FIG. 5. The retention ring 63 engaging the shoulder 64 prevents extension of the strut beyond a certain point, as in the previous embodiment.

In other respects the operation of the embodiment of FIG. 5 is the same as that of the first embodiment.

Referring now again to the diagrammatic showings of FIGS. 6-9, the relative positions of the components of the embodiment of FIGS. 1-4 are shown in greater detail. In accordance with the present invention, the balls are never manually engaged, nor are they engaged by any springs. The forces acting on any ball 26 for various conditions of the strut are diagrammatically shown in FIGS. 6-9, by means of arrows whose heads touch on the ball. FIG. 6 is the equilibrium or locked condition of the strut. Other arrows in the figures designate movement of strut components, either manually or under spring action. In FIG. 6, the arrow "a" indicates that the strut member 12 is about to be moved to the right. Thereafter, in FIG. 7, the arrow "b" indicates that the release collar or release member 34 is about to be moved to the left, this releasing movement having been completed in FIG. 8, as also indicated by the arrow "b"; the manual force on the collar or release member 34 is maintained as per the arrow "b", and the arrow "c" in this figure indicates that the strut member 12 is about to be moved to the left. In FIG. 9 the strut member 12 has been moved part way to the left, as per arrow " c", and manual force has been removed from the collar or release member 34, which now is under spring pressure indicated by the broken-line arrow "d".

FIG. 6 illustrates the equilibrium or locked condition of the strut. The arrows "e", "f" and "g" are the forces nominally present on the ball 26 when the ball is locked against movement. In FIG. 7 two arrows "h" and "i" are shown, which move the ball 26 as indicated by the arrow "j". The ball 26 now shifts to the position in FIG. 8, where the strut member 12 can be moved to the left while the collar or release member 34 is being held to the left against the action of its spring 38. In carrying out the initial part of this movement, the strut member 12 shifts the ball 26 laterally to the position of FIG. 9 and the strut member 12 is no longer restrained by the ball 26.

Still another embodiment of the invention is shown in FIGS. 10-14. FIG. 10 is a fragmentary axial section of an improved extendable and retractable, no-unlock-under-load strut construction which incorporates locking pieces in the form of arcuate locking dogs, that have been found by actual practice, to reduce point-contact loads which otherwise arise between the previously described strut, as a consequence of the engagement of the balls 26 with the inner strut member 12, for example.

Where hardened balls 26 had been employed in the previous construction, there was the possibility of their denting the inner strut member under high-load conditions. While the dents in of themselves did not lead to failure of the strut, their presence sometimes resulted in erratic sliding movement of the inner strut along its path of travel, due to the "bumping" effect of the dents as they by-passed one or more of the balls. Over prolonged periods of use, the bumping was deemed to be objectionable, for some applications.

In order to solve this problem, I have discovered that the use of elongate, arcuate locking dogs in place of the balls provides a relatively broad, expansive surface contact with the inner strut member. High-pressure point contacts are completely avoided, thus eliminating any tendency for the inner strut member to be dented. Significantly improved operation is realizeable especially over extended periods of use of the strut of FIGS. 10-11.

In the embodiment of FIGS. 10-14, like reference numerals have been assigned to parts corresponding to those of the embodiment of FIGS. 1-4 and FIGS. 6-9, with the suffix "b" added.

Referring now to FIGS. 10 and 11, there is illustrated the improved strut construction 10b as outlined above. It comprises an inner strut member 12b and an outer strut member 14b, the inner member 12b being adapted to telescope into the outer member 14b during collapse of the strut 10b.

The outer strut member 14b has three circumferentially spaced holes or through openings 24b constituting sockets, FIG. 11, which respectively carry and hold captive three locking pieces shown as being in the form of elongate, arcuate locking dogs 26b.

The inner strut member 12b has a tubular part 28b, and at its inner end, a threaded locking adapter or fitting 32b, screwed into the adjacent end of the tubular part 28b.

Slidably carried on the outer strut member 14 is a tubular release collar or release member 34b having a cylindrical bearing portion which is adapted for sliding engagement with the corresponding cylindrical surface of the outer strut member 14b. In the embodiment of FIGS. 10-14, a spiral compression spring similar to that designated 38 in FIG. 1, is employed, this spring having been omitted from FIG. 10 for clarity. As in the previous embodiment, it is disposed between the release collar or member 34b and the outer strut member 14b, to normally bias the release member 34b toward the right in FIG. 10.

By the present invention there is provided a new combination involving cooperable structures comprising arcuate dogs which effectively transmit to the release member 34b, load or force which is applied between the inner and outer strut members 12b, 14b, and which structures operate to forcibly retain the release member 34b against axial movement with respect to the outer strut member 14b, until such time as the load between the strut members 12b, 14b has first been essentially completely removed. In accomplishing this retention of the release member 34b, there are provided on the inner strut member 12b a shallow pocket 54b and a deep pocket 56b, the shallow pocket 54b extending axially for a somewhat shorter distance measured along the inner strut member 12b. There are also provided on the release member 34b, a shallow internal pocket 58b in the form of an annular internal groove, and a deep internal pocket 60b also in the form of an annular internal groove, displaced axially from the shallow internal pocket 58b of the release member 34b. Separating the pockets is an annular internal shoulder 62b. Depending on the locking or release condition of the strut, the three locking dogs 26b become seated in various ones of the pockets 54b, 56b, 58b, 60b in order to achieve the desired locking or release function.

As in the embodiment shown in FIGS. 1-4, the strut 10b is of a type which is extendable to a predetermined length, and thereafter locked in an extended position. The extended strut is especially adapted to remain locked so long as a compressive load is applied between the outer strut member 14b and the inner strut member 12b.

Referring now particularly to FIGS. 12-14, in accordance with the invention the locking dogs 26 are provided with a special configuration not heretofore existing in prior strut constructions. In a preferred method of fabrication of the dogs, each dog 26b is cut from ring stock (not shown) of the desired material, and thereafter precision machined to the particular configuration illustrated in these three figures.

The dog 26b has a generally convex outer face 65 and a concave inner face 66, these faces being respectively contoured to conform to and be complementary to the radius of curvature of the shallow pocket 58b of the release member 34b and the radius of curvature of the shallow pocket 54b of the inner strut member 12b. The face 65 is provided with bevels 68, which can be substantially flat and disposed at approximately a 45° angle with respect to the plane of curvature of the dog 26b. Additional bevels 70 are provided on the concave face 66 of the dogs. Also, by the invention, the opposite ends 72 of the dogs 26b are curved as shown, having a contour to enable each dog 26b to be received in and nest in its respective socket 24b. The ends of the sockets 24b are similarly curved, as shown in FIG. 11 by the indicated surface shading.

In a preferred embodiment, three locking dogs 26b are provided, each circumferentially spaced from one another by 120°, and uniformly spaced about the periphery of the outer strut member 14b.

Further in accordance with the present invention, cooperable keying means are provided between the release member 34b and the outer strut member 14b. This preferably takes the form of a pin and slot connection, the pin being designated 74 in FIG. 10, and the slot being indicated 76. The pin can be pressed in place, or secured by staking, or other means.

The operation of the embodiment of FIGS. 10-14 is generally similar to that described above in connection with the embodiment of FIGS. 1-4, with the exception that the point contact loads provided by the balls 26 is effectively eliminated by virtue of the broad faces 65, 66 of the arcuate locking dogs 26b. There is thus minimized any tendency for the inner strut member 12b or release member 26b to be dented over prolonged periods of heavy use, or in the event that lubrication of the sliding components of the strut deteriorates or otherwise is rendered ineffective.

The first-described embodiment of the invention shown in FIGS. 1-4 is seen to be especially economical to fabricate, since the locking pieces are in the form of simple balls which require no special fabricating steps during manufacture. The embodiment involving locking balls is thus especially adapted for economy where relatively light loads are applied to the strut member.

On the other hand, for more significant loads, the embodiment of FIGS. 10-14 is especially adapted to provide the needed strength and resistance to wear over extended periods of time. The locking dogs 26b which are employed, as substitutes for the balls 26 of FIGS. 1-4, can be readily cut and machined from ring stock, to provide the additional wear-resistance and with only minimal additional cost being incurred.

From the above it can be seen that I have provided novel and improved locking struts which feature significant advantages in safety of operation, while being straightforward in operation, and rugged and reliable in use even over extended periods of time. There are not required any special tools on the part of the operator; nor are there required special knowledge or skills in order to safely and effectively operate the struts.

The disclosed devices are thus seen to represent distinct advances and improvements in the field of extensible and collapsible struts.

Variations and modifications are possible without departing from the spirit of the invention.

Each and every one of the appended claims defines an aspect of the invention which is separate and distinct from all others, and accordingly it is intended that each claim be treated in this manner when examined in the light of the prior art devices in any determination of novelty or validity. 

What is claimed is:
 1. A strut comprising, in combination:a) outer and inner strut members being capable of extending or collapsing movements, the outer strut member having a socket, b) a locking piece captive and moveable in the socket, and c) a release member movable on the strut between locking and releasing positions, said release member having means to provide a shallow pocket and a deep pocket for respectively receiving, depending on its locking or releasing position, a portion of said locking piece, d) said inner strut member having a shallow pocket and a deep pocket to respectively receive another portion of said locking piece, e) said locking piece, socket of the outer strut member, and shallow pocket of the inner strut member restricting movement of the release member and restricting collapsing movement of the strut members when the release member is in its locking position wherein portions of the locking piece occupy the shallow pockets of both the release member and inner strut member, and alternatively enabling full collapsing movement of the strut members to be effected when the release member is in its releasing position and portions of the locking piece occupy the deep pocket of the release member, f) said pockets of the inner strut member enabling a limited relative movement of the strut members to be had for the purpose of freeing the locking piece for movement into the deep pocket of the inner strut member so as to enable the release member to be shifted from its locking position to its releasing position for permitting collapse of the strut.
 2. A strut construction as set forth in claim 1, wherein:a) said limited relative movement of the strut members is in an extending direction.
 3. A strut construction as set forth in claim 1, wherein:a) said limited relative movement of the strut members is in a collapsing direction.
 4. A strut construction as set forth in claim 1, wherein:a) the outer strut member has a plurality of sockets and locking pieces respectively moveable in and held captive in said sockets.
 5. A strut construction as set forth in claim 1, and further including:a) a fitting on the inner strut member, said fitting having the shallow and deep pockets of the inner strut member.
 6. A strut construction as set forth in claim 1, wherein:a) spring means are provided, biasing said release member to its locking position.
 7. A strut construction as set forth in claim 1, wherein:a) the release member has annular internal grooves constituting the said shallow and deep pockets thereof.
 8. A strut construction as set forth in claim 1, wherein:a) the inner strut member has exterior annular grooves constituting the said shallow and deep pockets thereof.
 9. A strut construction as set forth in claim 4, wherein:a) the release member has annular internal grooves constituting the said shallow and deep pockets thereof, b) said inner strut member having exterior annular grooves constituting the said shallow and deep pockets thereof.
 10. A strut construction as set forth in claim 1, wherein:a) the outer and inner strut members have cooperable stop means limiting the relative movement of the members to extended position.
 11. A strut construction as set forth in claim 1, wherein:a) the release member and the outer strut member have cooperable sealing means adjacent the ends of the release member, preventing ingress of foreign matter to the release member.
 12. A strut construction comprising, in combination:a) first and second strut members capable of relative movement between extended and collapsed positions, said first strut member having a socket and having a locking piece which is held captive in and which is moveable in the socket, b) a release member held captive and slidable on the strut construction between locking and release positions, said release member having a projecting shoulder adjacent to the socket, and c) camming shoulder means on said second strut member, normally holding said locking piece in a position in said socket so as to block the projecting shoulder of said release member and prevent releasing movement of the release member when the strut members are in extended position and under load, said camming shoulder means releasing said locking piece for unblocking movement of said locking piece in said socket in response to relative movement of said strut members in a direction in opposition to the load thereon, thereby to unblock the projecting shoulder of the release member and enable releasing movement thereof.
 13. The invention as set forth in claim 12, wherein:a) said locking piece blocks the shoulder of said release member in the manner of a locking bolt.
 14. A strut construction as set forth in claim 1, wherein:a) said locking piece comprises an arcuate locking dog received in the said socket.
 15. The invention as set forth in claim 1, wherein:a) the socket of the outer strut member is elongate in a circumferential direction, b) said locking piece comprising an arcuate locking dog carried in said elongate socket.
 16. The invention as set forth in claim 15, wherein:a) the outer strut member has two additional sockets, each being elongate in a circumferential direction, each of said additional sockets being circumferentially spaced from said first-mentioned socket, and b) additional arcuate locking dogs respectively carried in said additional sockets.
 17. The invention as set forth in claim 15, wherein:a) the opposite ends of the elongate socket are rounded, and b) the opposite ends of the locking dog are rounded and received respectively in the rounded ends of the elongate socket.
 18. The invention as set forth in claim 15, wherein:a) the arcuate locking dog has a generally concave face and a generally convex face, b) said concave face having a bevel along one edge.
 19. The invention as set forth in claim 18, wherein:a) the concave face has a bevel along the opposite edge.
 20. The invention as set forth in claim 15, wherein:a) the arcuate locking dog has a generally concave face and a generally convex face, b) said convex face having a bevel along one edge.
 21. The invention as set forth in claim 20, wherein:a) the arcuate locking dog has a generally concave face and a generally convex face, b) said convex face having a bevel along the opposite edge.
 22. The invention as set forth in claim 20, wherein:a) the shallow pocket of the inner strut member includes a substantially conical surface configuration, b) the bevel of the convex face of the arcuate locking dog having a configuration which is complementary to that of the conical surface, so as to distribute load from the locking dog and thus avoid high pressure contact points between the locking dog and the inner strut member, which might otherwise tend to dent the inner strut member.
 23. The invention as set forth in claim 15, wherein:a) said release member has an internal shoulder between said shallow and deep internal pockets thereof, b) said shoulder forming one wall of the shallow pocket of the release member, and said shoulder normally extending radially inside the outermost surface of the locking dog when the release member is disposed in its locking position.
 24. The invention as set forth in claim 15, wherein:a) said release member has an internal shoulder between the shallow and deep internal pockets thereof, b) said shoulder forming one wall of the deep pocket, and said one wall having a tapered configuration to facilitate by-pass of the locking dog by the release member when the latter moves from its release position to its locking position.
 25. The invention as set forth in claim 1, and further including:a) means keying the release member against turning with respect to the outer strut member while enabling limited relative sliding movement therebetween.
 26. The invention as set forth in claim 25, wherein:a) said keying means comprises a pin-and-slot connection between said release member and said outer strut member. 